The use of titanium implants and prosthodontic techniques in the preparation of non-human primates for long-term neuronal recording studies.

Investigators that require the chronic implantation of hardware on the non-human primate skull are often challenged with the possible failure of head implants. To improve the success rate of our head implants, titanium anchor screws, referred to as titanium endosseous implants, were implanted in the skulls of six macaques. Techniques adapted from the processing of dentures were utilized to pre-fabricate an acrylic "skull cap", which provided the mechanical support structure for our study-specific hardware. A two-stage procedure adapted from dentistry (Brånemark et al., 1977) was employed for the placement of titanium endosseous implants in the skull. This two-stage technique incorporates the principles of osseointegration and a healing period. Of the six skull-anchored implants prepared implementing the methods described in this paper, we have not experienced any failures. Additionally, all of the titanium endosseous implants examined post mortem were functionally successful (n=30). Histology results confirmed that there was healthy bone in direct contact with the titanium endosseous implants. The dense cortical bone of the macaque skull is ideal for the implantation of titanium endosseous implants. Titanium endosseous implants have provided secure, functional anchor points for the attachment of hardware to the macaque skull and have resulted in healthy, stable head implants that can remain on the skull for extended periods of time.

Implant-borne suture expansion in rabbits: a histomorphometric study of the supporting bone.

Osseointegrated implants have a large potential for diverse clinical applications, including support for sutural expansion and facial prostheses. The objectives of this study were to evaluate: (1) the histomorphometric response of thin cortical bone to implant placement and (2) whether loading of the bone surrounding these implants affects osseointegration as evaluated by histomorphometry. Eighteen New Zealand White rabbits had two titanium implants placed bilaterally in the anterior surface of their nasal bones. The rabbits were divided into an unloaded control group, one experimental group loaded at 1 Newton (N), and another loaded at 3 N. Fluorescent labels were used to mark areas of active bone formation. All rabbits were euthanized after 12 weeks of loading. Stereological point-hit and line-intercept methods were used to measure bone volume, direct bone-implant contact, new bone volume, and bone turnover rate in the bone surrounding the implants. All the implants remained stable during the loading period. A factorial ANOVA with repeated measures was used to compare the variables. The only significant difference among the three groups was a higher bone volume in the lateral coronal far region in the control group (p < 0. 05). Within all groups, bone volume (p < 0.002), turnover rate (p < 0.001), and percent of new bone (p < 0.05) were higher within 1 mm of the implant compared to 1-3 mm away. This may be due to the increased stress and strain in the bone adjacent to the implant. This study indicates that there are no detrimental effects of loading on osseointegration when implants placed in the thin facial cortices are used as anchors for sutural expansion.

Sutural expansion using rigidly integrated endosseous implants: an experimental study in rabbits.

Rigidly integrated implants offer great promise for orthodontic and orthopedic anchorage in the oral and midfacial regions. Rigid anchorage can be used to control unwanted tooth movement, provide abutments in edentulous arches, and open the vertical dimension of occlusion. To evaluate the use of endosseous implants in the midface region, two flanged titanium implants were placed on either side of the midnasal suture of 18 New Zealand White rabbits. The rabbits were divided into an unloaded control and two experimental groups. One experimental group was loaded at 1 Newton (N) and the other at 3 N. All rabbits were euthanized after 12 weeks of loading. Stereologic point-hit and line-intercept methods were used to analyze microradiographic and multiple fluorochrome histology of the suture. All implants remained stable during the loading period. The distance between the implants increased significantly in the loaded groups compared with the control, and was significantly higher in the 3 N group than in the 1 N group. Percent bone volume was significantly decreased, while the percent suture volume tended to be increased in the loaded groups. Mineral apposition and bone formation rates at the sutural surfaces were increased in the loaded groups (P < 0.05), but did not differ between loaded groups. These results indicate that relatively low loads (1 or 3 N) applied to rigidly integrated endosseous implants across an unfused suture are satisfactory for achieving expansion under the conditions of this study. The 3 N load resulted in slightly more expansion, but did not affect the rate of bone formation at the suture.